I like letting my faculties live till night in a deshabille; let us talk easily and sillily of the affairs of the day.
Ministers have acted most sillily in breaking up the burgher volunteers in large towns.
And so he stood, sillily smiling, until Richard Travis arose from his desk and came forward to meet her.
I was quite taken aback, and before I could find myself had sillily stammered, “I—I am a gentleman.”
Old English gesælig "happy, fortuitous, prosperous" (related to sæl "happiness"), from Proto-Germanic *sæligas (cf. Old Norse sæll "happy," Old Saxon salig, Middle Dutch salich, Old High German salig, German selig "blessed, happy, blissful," Gothic sels "good, kindhearted"), from PIE *sele- "of good mood; to favor," from root *sel- (2) "happy, of good mood; to favor" (cf. Latin solari "to comfort," Greek hilaros "cheerful, gay, merry, joyous").
This is one of the few instances in which an original long e (ee) has become shortened to i. The same change occurs in breeches, and in the American pronunciation of been, with no change in spelling. [Century Dictionary]The word's considerable sense development moved from "happy" to "blessed" to "pious," to "innocent" (c.1200), to "harmless," to "pitiable" (late 13c.), "weak" (c.1300), to "feeble in mind, lacking in reason, foolish" (1570s). Further tendency toward "stunned, dazed as by a blow" (1886) in knocked silly, etc. Silly season in journalism slang is from 1861 (August and September, when newspapers compensate for a lack of hard news by filling up with trivial stories). Silly Putty trademark claims use from July 1949.